CN101420239B

CN101420239B - Fm receiver

Info

Publication number: CN101420239B
Application number: CN2008101732321A
Authority: CN
Inventors: 小林启二
Original assignee: Sanyo Electric Co Ltd; Sanyo Semiconductor Co Ltd
Current assignee: Sanyo Electric Co Ltd; System Solutions Co Ltd
Priority date: 2007-10-24
Filing date: 2008-10-24
Publication date: 2012-07-25
Anticipated expiration: 2028-10-24
Also published as: EP2053753A2; CN101420239A; US8260233B2; US20090111410A1; EP2053753B1; JP2009105727A; EP2053753A3

Abstract

In a FM receiver, the passband width WF of band pass filter (IFBPF) is hard to set for sufficiently restraining all noises, voice distortions and adjacent interference under various states of received field strength, modulation degree and adjacent interference strength. The IFBPF can variably set WF and an attenuation slope KF. A bandwidth control circuit composed of hardware and receiving state composed of the combination of received field strength, modulation degree and adjacent interference strength controls the WF correspondingly. A microcomputer controls KF according to a program stored in a non-volatile memory for executing effective fine adjustment to the passband width. The voice distortion prevention and WF control contradictory to the adjacent interference are required in the ebb electric field state when high modulation and adjacent interference exist thereby miniaturizing the setting. Specially a better receiving state can be obtained through altering the structure of KF through a program under this state.

Description

The FM receiver

Technical field

The present invention relates to a kind of reception by the FM receiver of the signal of frequency modulation (Frequency Modulation:FM).

Background technology

Because the FM signal is according to the frequency of change carrier waves such as voice signal, so frequency band that for example need be wideer than AM signal in the transmission of FM signal.Therefore; In the FM receiver; Under situation about receiving as the transmission signals of target, receive easily from interference (adjacent interference) near other signal of the frequency transmission of its frequency, the quality of the voice signal that this obtains carrying out detection sometimes produces harmful effect.Can reduce this adjacent interference as the frequency band of the band pass filter (Band Pass Filter:BPF) of the signal (desirable ripple) of receiving target through dwindling extraction.

Fig. 3 is the block diagram that the structure of FM receiver in the past is described.(Radio Frequency: radio frequency) signal is intermediate frequency (Intermediate Frequency:IF) f with regulation by frequency translation to the RF that is received by antenna _IFM signal, and be imported into IFBPF2.IFBPF2 is with f _IFBe the band pass filter of centre frequency, constitute the pass band W that for example in the scope of about 40kHz～about 220kHz, can change IFBPF2 _F

The FM signal that has passed through IFBPF2 is provided for limiting amplifier 4.The amplitude of 4 pairs of FM signals of limiting amplifier amplifies as square wave, removes the noise that is mixed in the FM signal.Amplify and be imported into FM detecting circuit 6 by limiting amplifier 4 as the FM signal of square wave.The output signal of 6 pairs of limiting amplifiers 4 of FM detecting circuit carries out the FM detection.

Export reproduced sound signal according to this FM detection.In addition, FM detection output S _DETBe imported into adjacent interference testing circuit 8 and modulation degree testing circuit 10.Adjacent interference testing circuit 8 is from S _DETIn extract because adjacent interference and issuable radio-frequency component, generate the direct current signal S of correspondent voltage level strong and weak with it _AIModulation degree testing circuit 10 is according to S _DETGenerate direct current signal S with the modulation degree correspondent voltage level that receives signal _MD

Limiting amplifier 4 also is connected on signal strength meter (S meter) circuit 12.Limiting amplifier 4 is made up of the circuit that the multi-buffer amplifier is connected in series.S intensitometer circuit 12 as input signal, generates signal strength signal intensity corresponding reception electric field intensity signal S with FM signal according to these input signals with the output of each buffer amplifier of limiting amplifier 4 _FI

Bandwidth control circuit 14 is transfused to the output S of adjacent interference testing circuit 8 _AI, modulation degree testing circuit 10 output S _MD, and the output S of S intensitometer circuit 12 _FI, according to the pass band W of these signal controlling IFBPF2 _F Bandwidth control circuit 14 is controlled and is made the output signal S of adjacent interference testing circuit 8 _AIThe high more bandwidth W that makes of level _FNarrow more.Thus, the FM signal of removing behind the adjacent interference ripple is input to FM detecting circuit 6, the deterioration of the sound quality that can reduce, suppress to cause by adjacent interference.

In addition, even being at received electric field strength under the situation of weak electric field state of regulation, bandwidth control circuit 14 also controls with reduced bandwidth W _FThus, can reduce weak electric field noise contribution, and realize the raising of sensitivity through IFBPF2.

On the other hand, under the state of high modulation, as reduced bandwidth W _FThe time might produce audio distortions.Therefore, under the situation that does not produce adjacent interference and lofty tone system, even be in the weak electric field state, bandwidth control circuit 14 is also with bandwidth W _FBe set at reference bandwidth, compared with removing the weak electric field noise, more preferably sound-inhibiting distortion.

Patent documentation 1: TOHKEMY 2004-312077 communique

Summary of the invention

The problem that invention will solve

Under the situation of the situation of weak electric field and high modulation, on the basis that obtains preferable sound quality for pass band W _FControl be opposite.Therefore, under the inhibition of the minimizing of weak electric field noise and audio distortions compromise, set W _F, be difficult to carry out preferable setting.And, as stated, W _FSetting also be related to the intensity of adjacent interference, for example, even can under the situation that does not have weak electric field and high modulation under the state of adjacent interference, preferably set W _F, have under the state of adjacent interference this W _FAlso may not preferably remove adjacent interference.On the other hand, in the bandwidth control circuit that constitutes by hardware 14 in the past, be not easy W for these various conditions _FBe adjusted to preferable value, then make the structure of bandwidth control circuit 14 become complicated if carry out this adjusting.That is, there was following problem: under the various states of received electric field strength, percentage modulation and adjacent interference intensity, be difficult to set W in the past _FWith all noises of abundant inhibition, audio distortions and adjacent interference, only can set W _FSuitably to satisfy certain characteristic.

The present invention accomplishes in order to address the above problem a little, and its purpose is to provide a kind of FM receiver of easy realization good sound quality.

The scheme that is used to deal with problems

FM receiver involved in the present invention has: the M signal generative circuit, and its carrier frequency shift of carrying out with receiving target FM signal to received signal is the frequency translation of the intermediate frequency of regulation, generates M signal; Band pass filter, the through characteristic parameter that it can set the regulation that comprises pass band is changeably passed through the above-mentioned receiving target FM signal that is transformed to above-mentioned M signal; The receiving intensity testing circuit, it detects received electric field strength according to above-mentioned M signal; The modulation degree testing circuit, it detects the modulation degree of above-mentioned receiving target FM signal; The adjacent interference testing circuit, it detects the interference of adjacent signals for above-mentioned receiving target FM signal; Bandwidth control circuit; It carries out and control by the concern accepting state relevant provisions that constitutes of the interference strength of above-mentioned received electric field strength, above-mentioned percentage modulation and above-mentioned adjacent signals, and above-mentioned pass band is set at and the corresponding primary bandwidth of above-mentioned concern accepting state; Storage part, the control program of above-mentioned through characteristic parameter control process is controlled in its storage decision according to above-mentioned interference strength and above-mentioned modulation degree; And microcomputer, it carries out above-mentioned control program, and the auxiliary pass band of the width of the auxiliary passband of the conduct of the both sides that are attached to the passband of being set by above-mentioned bandwidth control circuit is controlled.

The effect of invention

According to the present invention, be the basis with the primary bandwidth that can set by the bandwidth control circuit that hardware constitutes, microcomputer is according to control program adjustment pass band W _FCarry out this adjustment through the additional auxiliary passband of the primary bandwidth that bandwidth control circuit is set.At this, the pass band of band pass filter is meant that generally the gain with respect to passband becomes-high frequency side of 3dB, the width between the lower frequency side cut-off frequency separately, is referred to as the pass band of narrow sense.Therewith relatively, at this, with passband, and be present between this passband and the attenuation band and can make the transition band that signal energy partly passes through and merge the pass band that the frequency band that obtains is called broad sense.In the present invention, the additional pass band that can change narrow sense of the auxiliary passband of being undertaken by microcomputer in addition, also can be adjusted width or the passband of transition band and the pass band that transition band width separately changes broad sense.In addition, can regulate the width of transition band according to attenuation slope.Can change the adjustment of the pass band of the narrow sense of being undertaken by microcomputer or broad sense according to control program neatly, and compare through the adjustment of pass band bandwidth control circuit, that utilize hardware, the degree of freedom is higher.Therefore, for the various combinations of the interference strength of received electric field strength, percentage modulation and adjacent signals, with the situation property of only being undertaken by bandwidth control circuit than more easily realizing preferable reception.

Description of drawings

Fig. 1 is the summary module structure chart of the related FM radio receiver of execution mode of the present invention.

Fig. 2 is explanation W _FAnd K _FThe key diagram of basic controlling action.

Fig. 3 is the block diagram that the structure of FM receiver in the past is described.

Description of reference numerals

The 50:FM radio receiver; The 52:FM tuning circuit; 54: microcomputer; 56: system bus; 58: antenna; 60: nonvolatile memory; The 62:RF circuit; 64: the first local oscillating portions; 66: the first hybrid circuits; 68,72:BPF; 70,78: buffer amplifier; 74: the second local oscillating portions; 76: the second hybrid circuits; 80:IFBPF; 82: limiting amplifier; The 84:FM detecting circuit; 86: matrixer; 92:S intensitometer circuit; 94: quality (Quality) sensor circuit; 96: the adjacent interference noise extraction circuit; 98: the modulation degree signal generating circuit; The 100:SD circuit; 102: bandwidth control circuit; 104: register; 106: ON-OFF control circuit; 110,120:HPF; 112,122,126: detecting circuit; 114: comparator; 124:LPF.

Embodiment

Below, according to description of drawings execution mode of the present invention (below be called execution mode).Fig. 1 is the summary module structure chart of the related FM radio receiver 50 of execution mode.This FM radio receiver 50 be comprise FM tuning circuit 52, the microcomputer 54 that the action of this FM tuning circuit 52 is controlled, the FM radio receiver that can carry out the system bus 56 of the communication between them as control part.The major part of FM tuning circuit 52 for example will be from the RF signal S that is received by antenna 58 by ICization _RFOGenerate the output signal S corresponding with the voice signal in hope radio station _OUTSignal processing circuit and the nonvolatile memories such as EEPROM 60 of preserving the data in the action of this signal processing circuit, used etc. constitute IC, or the different chip of a chip or an encapsulation.

Handle the RF signal S that receives by antenna 58 through signal processing system _RFO, generate output signal S _OUTWherein, above-mentioned signal processing system comprises the local oscillating portion of the local oscillating portion of RF circuit 62, first 64, first hybrid circuit 66, band pass filter (BPF:Band PassFilter) 68,72,

buffer amplifier

70,78, second 74, second hybrid circuit 76, IFBPF80, limiting amplifier 82, FM detecting circuit 84 and matrixer (MPX circuit) 86.

FM tuning circuit 52 also comprises S intensitometer circuit 92, quality sensor circuit 94, adjacent interference noise extraction circuit 96, modulation degree signal generating circuit 98, SD (Station Detection: the radio station is detected) circuit 100, bandwidth control circuit 102, register 104 and ON-OFF control circuit 106 except comprising the said structure key element.

RF signal S _RFOBe imported into RF circuit 62.RF circuit 62 carries out following tuning processing: from spreading all over the RF signal S of whole reception object frequency band _RFOIn extract to comprise and have carrier frequency f _RTarget receive the RF signal S of the narrower frequency band in radio station _RFThe RF signal S that extracts by RF circuit 62 _RFBe imported into first hybrid circuit 66.

The first local oscillating portion 64 comprise used PLL (Phase Lock Loop: phase-locked loop) oscillating circuit of circuit and frequency dividing circuit, export the first local oscillation signal S _LO1

The RF signal S that first hybrid circuit 66 will be transfused to _RFWith the first local oscillation signal S from first local oscillating portion 64 inputs _LO1Mix, generate the first M signal S _IF1Adjustment S _LO1Frequency f _LO1Make and be included in S _RFIn target receive the carrier frequency f of the signal in radio station _RThrough undertaken by first hybrid circuit 66 to S _IF1Frequency translation and be transformed to the first intermediate frequency f of regulation _IF1Carry out this adjustment as follows: microcomputer 54 is setting data in not shown register, according to the frequency of oscillation of the oscillating circuit in this Data Control first local oscillating portion 64, the frequency dividing ratio of frequency dividing circuit.The first intermediate frequency f _IF1For example be set to 10.7MHz.

S from 66 outputs of first hybrid circuit _IF1Be imported into second hybrid circuit 76 through BPF68, buffer amplifier 70 and BPF72.For example, can use ceramic filter to constitute BPF68,72.

The first M signal S that second hybrid circuit 76 will be transfused to _IF1With the second local oscillation signal S from second local oscillating portion 74 inputs _LO2Mix, generate the second intermediate frequency f _IF2The second M signal S _IF2S _LO2Frequency f _LO2Be set to (f _IF1-f _IF2), be included in S _IF1In frequency f _IF1Target receive signal and in second hybrid circuit 76, be transformed to frequency f _IF2The second intermediate frequency f _IF2For example be set to 450kHz.

S _IF2Be imported into IFBPF80 via buffer amplifier 78.IFBPF80 is with f _IF2For centre frequency and can set changeably and comprise pass band W _FWith attenuation slope K _FThe band pass filter of through characteristic parameter.Basically control the pass band W of IFBPF80 by bandwidth control circuit 102 _FIn addition, control attenuation slope K as follows _F: for example in IFBPF80, prepare multistage BPF, switch their connection progression, perhaps use control voltage to change the circuit constant of BPF with switch.For example, in Fig. 1, as being used to control attenuation slope K _FCircuit, the ON-OFF control circuit 106 that illustration is controlled the switch of the connection progression that switches BPF.Further record and narrate the through characteristic parameter control of this IFBPF80 after a while.

S from IFBPF80 output _IF2Be imported into FM detecting circuit 84 through limiting amplifier 82.FM detecting circuit 84 for example is made up of quadrature (quadrature) detecting circuit.84 couples of S of FM detecting circuit from limiting amplifier 82 inputs _IF2Carry out the FM detection, output detection output signal S _DET

When carrying out stereophonic broadcasting, matrixer 86 is from the S as stereophonic composite signal _DETIn extract (L+R) signal, (L-R) signal respectively, from these (L+R) signals and (L-R) signal, isolate L signal and the R signal line output of going forward side by side through the matrixing mode.

S intensitometer circuit 92 is for example according to the S from the BPF72 input _IF1Generate and be included in S _IF1In variance components signal S _M-AC, and this variance components smoothing is generated reception electric field intensity signal S through low pass filter (Low PassFilter:LPF) _M-DCIn quality sensor circuit 94, utilize S _M-ACOn the other hand, in SD circuit 100 and bandwidth control circuit 102, utilize S _M-DC

Quality sensor circuit 94 is according to S _M-ACThe circuit that detection has or not adjacent interference, multipath to disturb comprises high pass filter (High Pass Filter:HPF) 110, detecting circuit 112 and comparator 114.HPF110 can be according to from S _M-ACIn extract with adjacent interference frequency band corresponding composition with multipath and disturb which the situation in the frequency band corresponding composition, switch cut-off frequency f _CAbout adjacent interference, when the broadcasting station that will cause adjacent interference and hope the RF frequency between the radio station difference when being made as △ f, the S when adjacent interference takes place _M-ACThe radio-frequency component of middle appearance and △ f correspondent frequency.For example, the channel spacing of the FM broadcasting of Japan is 100kHz, therefore can be with from S _M-ACIn the cut-off frequency f of HPF110 when extracting with the corresponding composition of adjacent interference _CFor example be made as about 100kHz.In addition, general, disturb the frequency of the radio-frequency component that causes so high by multipath unlike the composition that causes by adjacent interference, therefore can be with from S _M-ACIn extract the f when disturbing corresponding composition with multipath _CBe set at about 50kHz.The radio-frequency component that 112 pairs of detecting circuits have passed through HPF110 carries out rectification, the adjacent interference noise contribution amount in generation and the reception signal or the direct current signal V of multipath noisiness correspondent voltage level _SQAt this, of the back, at the pass band W that carries out IFBPF80 through bandwidth control circuit 102 _FAutomated variable control in utilize V _SQ

Comparator 114 is with the output level V of detecting circuit 112 _SQWith the reference voltage V that is set to defined threshold _Ref1Compare, for example, if V _SQ>V _Ref1, then export the SQ sensor signal S that the judged result of adjacent interference or multipath interference has taken place as expression the H level _SQ, on the other hand, if V _SQ≤V _Ref1, then export the S that the judged result of adjacent interference, multipath interference does not take place as expression the L level _SQThis S _SQBe imported into microcomputer 54.

Adjacent interference noise extraction circuit 96 is extracted the output signal S that is included in FM detecting circuit 84 _DETIn the adjacent interference noise contribution.S when adjacent interference takes place _DETHave radio-frequency component, this radio-frequency component is superimposed in the signal component of the voiceband corresponding with hope radio station, have and hope the RF difference on the frequency △ f correspondent frequency between radio station and the interfering station.Adjacent interference noise extraction circuit 96 comprises HPF120, detecting circuit 122, output with because the direct current signal S of the strong and weak correspondent voltage level of adjacent interference and issuable radio-frequency component _AIThe cut-off frequency f of HPF120 _CBe set to and be included in S _DETIn the main component of adjacent interference noise pass through HPF120.For example, with above-mentioned HPF110 likewise, can be with the cut-off frequency f of HPF120 _CFor example be made as about 100kHz.S _AIBe imported into bandwidth control circuit 102.

Modulation degree signal generating circuit 98 is according to S _DETGenerate direct current signal S with the modulation degree correspondent voltage level that receives signal _MDModulation degree signal generating circuit 98 comprises LPF124, detecting circuit 126, removes the radio-frequency component that is caused by adjacent interference etc., the direct current signal S of output and modulation degree correspondent voltage level _MDIn bandwidth control circuit 102, utilize S _MD

Whether the 100 output expressions of SD circuit detect the SD signal S that receives the radio station with the tuned frequency that sets _SDThe reception electric field intensity signal S that SD circuit 100 is judged from S intensitometer circuit 92 _M-DCThe threshold value that whether surpasses regulation.In addition, SD circuit 100 is according to M signal S _IF2Frequency f and detection output S _DETVoltage V between the f-V conversion characteristics that is called as the S curve, whether the frequency band that judge to receive the radio station is present in the frequency band (SD frequency band) as target.SD circuit 100 obtains in the SD frequency band under the situation of reception signal of prescribed strength, is judged as to detect to receive the radio station.Output S according to this SD circuit 100 _SDCan grasp received electric field strength and whether surpass setting.In addition, switch the width of SD frequency band, can either judge that detecting the radio station is that institute hopes also can utilize as the detecting unit that has or not adjacent interference in radio station or adjacent radio station according to the radio station detected state under each bandwidth.

Bandwidth control circuit 102 is according to the V that obtains from quality sensor circuit 94 _SQOr the S of adjacent interference noise extraction circuit 96 generations _AI, from the S of modulation degree signal generating circuit 98 _MD, and the S that generated of S intensitometer circuit 92 _M-DCGrasp accepting state.In addition, can also be according to the output S of SD circuit 100 _SDGrasp having or not of received electric field strength in this accepting state, adjacent interference.Bandwidth control circuit 102 generates the control voltage that is predetermined by its circuit structure basically according to the combination of strength of received electric field strength, percentage modulation adjacent interference.And, through its control voltage signal S _WFControl the W of IFBPF80 _F

Specifically, bandwidth control circuit 102 is controlled and is made V _SQOr S _AISignal level high more, make bandwidth W _FNarrow more.Thus, be input to FM detecting circuit 84, can reduce, suppress because the deterioration of the sound quality that adjacent interference causes with removing the FM signal that the adjacent interference ripple obtains.In addition, can be following structure also: with V _SQOr S _AICompare with the threshold value of regulation, if V _SQOr S _AIThen be judged as greater than this threshold value and be in adjacent interference state (disturbance state is arranged), control and dwindle W _F, on the other hand,, control and make W if be in non-adjacent interference state (noiseless state) with next being judged as in threshold value _FBroaden.

In addition, bandwidth control circuit 102 is according to S _MDJudge whether modulation degree is in the high modulation state of regulation.If S _MDGreater than the regulation threshold value then be made as the high modulation state that is in, on the other hand, if in threshold value with the next low modulation state that is in that is judged as.

In addition, bandwidth control circuit 102 is according to S _M-DCJudge whether received electric field strength is in the weak electric field state of regulation.If S _M-DCThe threshold value that is lower than regulation then is made as the weak electric field state that is in, on the other hand, if more than threshold value would be judged as be in more than the electric field.

Register 104 is connected on the system bus 56.Set the control data D that is used to carry out the assist control relevant from microcomputer 54 through 56 pairs of registers of system bus 104 with the passband of IFBPF80 _SBRecord and narrate this control data D after a while for register 104 _SBSetting.

ON-OFF control circuit 106 is according to being kept at the data D in the register 104 _SBControl the switch in the IFBPF80, change constitutes the connection progression of the BPF of IFBPF80.

Microcomputer 54 is through system bus 56, based on I ²C (Inter-IntegratedCircuit: communication unit of agreement etc. internal integrated circuit); Obtain the information relevant from various sensor circuits such as quality sensor circuit 94, adjacent interference noise extraction circuit 96, modulation degree signal generating circuits 98 with accepting state; On the other hand, for example control the action of the each several part in the FM tuning circuits 52 through system bus 56.

Nonvolatile memory 60 is connected on the system bus 56.Nonvolatile memory 60 is for example by EEPROM (Electronically Erasable and ProgrammableRead Only Memory: Electrically Erasable Read Only Memory) constitute.Can rewrite the memory contents of nonvolatile memory 60 according to the signal that provides from the outside.On the other hand, read the data that are written into by microcomputer 54.

In addition, microcomputer 54 moves according to program, and this program is stored in the nonvolatile memory 60.Nonvolatile memory 60 is preserved the exercises control program of the action that is used to control FM tuning circuit 52, and microcomputer 54 suitably reads in these programs and carries out.Especially, in this execution mode, microcomputer 54 is according to the program that is kept in the nonvolatile memory 60, with the accepting state of the FM tuning circuit 52 data D of rewrite register 104 correspondingly _SB, thus, the for example attenuation slope K of control IFBPF80 _FFurther record and narrate this point after a while.

Then, the pass band W that is undertaken by bandwidth control circuit 102 and microcomputer 54 is described _FWith attenuation slope K _FControl action.Fig. 2 is explanation W _FAnd K _FThe key diagram of basic controlling action.The figure shows the W in each combination (condition stub) of power of height and received electric field strength of the having or not of adjacent interference, modulation degree _FWidth and K _FSize.At this, about undertaken by bandwidth control circuit 102 for the W that states after the adjacent interference _FControl, though can be according to S _AISignal level change W continuously _FGround is controlled, but in Fig. 2, for ease, is divided into and S _AIWhether greater than the corresponding adjacent interference state of situation of the threshold value of regulation and two states of non-adjacent interference state.

(a) of Fig. 2 representes the condition stub group of weak electric field state, the condition stub group of the state during (b) of Fig. 2 representes with sheet form more than the electric field with sheet form.(a) of Fig. 2 and (b) of Fig. 2 have four hurdles of two row two row corresponding with the combination that has or not of the height of modulation degree and adjacent interference respectively.

In these each hurdles, show the pass band W that controls by bandwidth control circuit 102 basically _FThe attenuation slope K that controls through ON-OFF control circuit 106 of definition value and microcomputer 54 _FDefinition value.In addition, W _FValue ww represent standard bandwidth, w _N1, w _N2The narrow bandwidth that expression is narrower than standard bandwidth ww.Basically, even standard bandwidth ww receives the wide bandwidth that signal is the also very difficult generation audio distortions of high modulation, on the other hand, narrow bandwidth w _N1, w _N2It is the width that to expect to remove the effect of adjacent interference.In addition, establish attenuation slope K _FStandard value be k _L, k _HBe k _H>k _LThe overdamp slope.That is, at k _HBe set to attenuation slope K _FState under, with standard attenuation slope k _LBe set to attenuation slope K _FCompared, become sharply the narrowed width of transition band in the decay of transition band.

Bandwidth control circuit 102 is controlled for the influence that reduces adjacent interference and to be made pass band W basically under the adjacent interference state _FThan reference tape width (W _F=w _NI), on the other hand, under non-adjacent interference state,, constitute pass band W from the viewpoint that gets rid of sound distortion _FBe set at reference bandwidth (W _F=ww).In addition, under the weak electric field state, preferably dwindle pass band W _FTo reduce the weak electric field noise and to improve sensitivity.From this viewpoint, under the low modulation state of the very difficult generation audio distortions of bandwidth control circuit 102 in the weak electric field state, for example no matter have or not adjacent interference, all with W _FBe set at w _N2At this, as stated, w _N2Be the value that to expect to remove the effect of adjacent interference, and be the value that to expect to suppress the weak electric field anti noise, can set w for basically _N2≤w _N1

On the other hand, microcomputer 54 moves according to the program that is kept in the nonvolatile memory 60.Through rewriteeing this program, for example, can freely define K to each above-mentioned class condition _FBe made as k _LAnd k _HIn which.For example; Be made as suitable state as the basis time for state that bandwidth control circuit 102 is realized; Under the situation of weak electric field state; Accepting state is divided into four condition stubs shown in (a) of Fig. 2, the i.e. non-adjacent interference state in situation, (2) and situation, (4) adjacent interference state and the situation of system state to a high-profile of situation, (3) adjacent interference state and the low-key system state of system state to a high-profile of (1) non-adjacent interference state and low-key system state, will defines K _FProgram register in the nonvolatile memory 60, and microcomputer 54 is carried out.

For example, in the situation of above-mentioned (1), (3), be under the situation of low-key system state, be set at K _F=k _HThus, particularly in the situation of (3), be under the situation of adjacent interference state and low-key system state, can keep the narrow bandwidth w that utilization is set by bandwidth control circuit 102 _N2The effect of the preferable inhibition adjacent interference that obtains.

On the other hand, in the situation of above-mentioned (2), be non-adjacent interference state and to a high-profile under the situation of system state, be set at K _F=k _LThus, can keep or strengthen the effect of the sound-inhibiting distortion that standard bandwidth ww that utilization set by bandwidth control circuit 102 obtains.

In the situation of above-mentioned (4), be adjacent interference state and to a high-profile under the situation of system state, set k _HAnd k _LAmong for example the selected side of manufacturer of FM radio receiver 50 as K _FFor example, under the bigger situation of the modulation degree of the FM of the use state of FM radio receiver 50 broadcasting, because adjacent interference and possibly make the influence of audio distortions become big, so k selects in manufacturer _LTransition band is broadened, can preferentially alleviate audio distortions, on the contrary, under the so not big situation of the modulation degree of territory of use, select k _H, be made as the state that dwindles transition band, can preferentially reduce adjacent interference.In addition, manufacturer from desirable tonequality, with the points such as compatibility of the late-class circuit of FM tuning circuit 52 on can select to obtain the K of better tonequality _F

In addition, can realize K through the connection progression that changes the BPF that constitutes IFBPF80 _FChange.Specifically, dwindle the width of transition band, so the structure of ON-OFF control circuit 106 control IFBPF80 makes at K through the progression that increases BPF _FIncrease the progression that is connected in series of BPF during increase, on the contrary, at K _FControl the feasible progression that reduces during minimizing.

According to the present invention, be kept at the program in the nonvolatile memory 60 through change, make by hardware to constitute and the structure of the bandwidth control circuit 102 that afterwards is difficult to change in statu quo just can realize the optimization of accepting state.The program that is stored in the nonvolatile memory 60 through replacement also can realize K _FChange, but this program can be following structure also for example: read in the parameter that is set in addition in the nonvolatile memory 60, can switch K according to this parameter _FIn this case, just can change K as long as rewrite parameter _F

In addition, for example about output S like quality sensor circuit 94 _SQ, SD circuit 100 output S _SDSuch transducer output that is changed into H level/L level by two-value, microcomputer 54 can directly be taken into from the I/O port in processing.On the other hand, about using like S _M-DC, S _AI, S _MDThe transducer output that such analog signal obtains; (Analog-to-Digital: analog digital) translation circuit (ADC) is transformed to numerical data through A/D; This numerical data is input to microcomputer 54; On software, carry out threshold decision through microcomputer 54, can judge whether to the weak electric field state, be high modulation or low modulation and have or not adjacent interference.In addition, also can be with analog signal being carried out the structure that result that threshold decision obtains is input to microcomputer 54 through comparator.

In addition, W _F, K _FSwitching controls can be through making it have the structure that time constant, hysteresis quality prevent to produce continually at a high speed the situation of switching.Thus, can suppress to produce the change of sound shake or the tonequality uncomfortable phenomenon of audience that makes such as remarkable.

Claims

1. FM receiver is characterized in that having:

The M signal generative circuit, its carrier frequency shift of carrying out with receiving target FM signal to received signal is the frequency translation of the intermediate frequency of regulation, generates M signal;

Band pass filter, the through characteristic parameter that it can set the regulation that comprises pass band is changeably passed through the above-mentioned receiving target FM signal that is transformed to above-mentioned M signal;

The receiving intensity testing circuit, it detects received electric field strength according to above-mentioned M signal;

The modulation degree testing circuit, it detects the modulation degree of above-mentioned receiving target FM signal;

The adjacent interference testing circuit, it detects the interference of adjacent signals for above-mentioned receiving target FM signal;

Bandwidth control circuit; It carries out and the concern accepting state relevant provisions that constitutes control by the interference strength of above-mentioned received electric field strength, above-mentioned percentage modulation and above-mentioned adjacent signals, and above-mentioned pass band is set at and the corresponding primary bandwidth of above-mentioned concern accepting state;

Storage part, its storage control program, this control program decision is controlled above-mentioned through characteristic parameter control process according to above-mentioned interference strength and above-mentioned modulation degree; And

Microcomputer, it carries out above-mentioned control program, to the both sides that are attached to the passband of setting by above-mentioned bandwidth control circuit, control as the auxiliary pass band of the width of auxiliary passband,

Wherein, the noiseless state of the not enough specified reference value of above-mentioned interference strength and above-mentioned modulation degree are set for than above-mentioned modulation degree greater than the above-mentioned auxiliary pass band under the situation of the high modulation state of the threshold value of regulation is that the situation of the low modulation state below the threshold value of afore mentioned rules is wideer to above-mentioned control program.

2. FM receiver according to claim 1; It is characterized in that above-mentioned control program is that above-mentioned auxiliary pass band under the situation that disturbance state and above-mentioned high modulation state are arranged more than the said reference value is set for wideer than the situation of above-mentioned low modulation state with above-mentioned interference strength also.

3. FM receiver according to claim 1 and 2 is characterized in that,

Above-mentioned band pass filter can be set attenuation slope changeably,

Above-mentioned control program comprises the control procedure of controlling above-mentioned attenuation slope according to above-mentioned interference strength and above-mentioned modulation degree,

As the control of above-mentioned auxiliary pass band, above-mentioned microcomputer changes the width of transition band according to above-mentioned attenuation slope.